The long range objectives of the proposed research is to better understand the contribution of renal free fatty acid (FFA) transport and metabolism to overall lipid homeostasis. In this light, a primary objective is to determine whether or not FFA are transported by an organic acid transport system. An isolated perfused rat kidney will be used for many experiments since effects of hormones and levels of oxogenous substrates can be controlled. Since FFA are extensively metabolized by the kidney, we will study FFA transport into renal tubular cells and simultaneously, identify and quantitate the products of FFA metabolism. In order to study FFA without the complications of simultaneous metabolism, we will use preparations of isolated membrane vesicles derived from luminal and antiluminal membranes of rat renal tubular cells. Finally, we will study whether lipid abnormalities which occur in some pathological conditions, such as uremia or immunosuppressive drug treatment, may be explained in terms of altered cellular FFA transport and metabolism.